This invention relates to a reflected-wave maser structure, and more particularly to a dielectrically loaded microwave circulator for cryogenically cooled maser waveguide structures cascaded for high net gain and wide bandwidth.
A plurality of reflected-wave maser structures can be cascaded in one housing using three-port coupling circulators and isolators or four-port circulators in a volume of conductive material, such as copper. Reduced size permits use of more cascaded structures for more net gain and wider bandwidth compared to the disclosure in U.S. Pat. No. 3,978,417.
In the prior art, a reflected-wave maser is connected to one port of each coupling circulator. Two other ports of the coupling circulator are employed as input and output ports of a reflected-wave maser. The output port of one circulator is coupled to the input port of another circulator through an isolator which may be comprised of a three-port circulator having one port terminated by an absorbing load. It would be desirable to reduce the size of such an arrangement of reflected-wave masers and circulators, such as for X-band and K-band use. For example, at 9 GHz the width of the vacuum or air filled waveguides must be about one inch. Use of dielectric loading can reduce the waveguide width to 1/4 inch at 9 GHz. Use of four-port, rather than three-port circulators reduces the size even more by diminating a number of isolators required.